The goals of this program are to extend our understanding of the biology and application of dendritic cells(DC) in tumor immunology, and to examine their potential tolerogenic role(s) in autoimmune disease and transplantation. In each case there is a fundamental need to define the potential role of DC's in these processes. The role(s) of the imaging core are diverse. In summary we will examine protein expression by dendritic cells, examine dendritic cell trafficking and location within tissue systems, and define morphologic and immunocytochemical markers for different populations of DCS. This identification varies from the low resolution studies of whole tissues, defining dendritic cell tracking, to high resolution observations of successful gene incorporation as well as upon culture suggests that visualization of morphology, processes and phenotype will provide important clues to their functional differences not available from other sources. The Structural Biology Imaging Center, in which this core service will be performed, is designed with this function in mind. It is equipped to perform a continuum of optical methods including all types of light and electron microscopy essential to this program project. Within the scope of this project at the light microscopic levels this include: histological, immuno-histological live cell and in situ hybridization technologies. At the electron microscopic level we will provide fine structural and immuno-electron microscopic evaluation of specimens as a natural extension of the light microscopic analyses when needed. Furthermore, our considerable experience in computerized image processing and morphometry will allow quantitative analyses of observed phenomena to corroborate earlier, possibly quite subtle qualitative changes. This core will be used extensively by all projects, though the imaging tools used will vary from project to project. Preliminary data have shown the validity of these approaches, and we expect a very significant increase in the use of optical techniques within the formal setting of this program.